Patent GB-417269-A (GB)
Title: Improvements in speed change mechanism for lathes and like machine tools
IPC: B23Q5/14
Filed: 1933-04-13
Abstract: 417,269. Speed-controlling mechanism for lathes. CRAVEN BROS. (MANCHESTER), Ltd., Vauxhall Works, near Stockport, and RIVERS, J. H., Springfield, Altrincham Road, Gatley, both in Cheshire. April 13, 1933, No. 11070. [Class 83 (iii).] In lathes and like machines wherein it is desired to vary the spindle speed according to the radius at which the tool is operating, or according to the particular tool brought into use at any stage of the cycle of operations of the machine, change speed gearing is provided for the spindle drive of the type wherein a member adapted to bring a number of gears of different ratios into operation successively is intermittently coupled to a power-driven shaft, said coupling means, according to the invention, comprising a clutch actuated by one arm of a three-armed lever, the second arm being intermittently held and released by means operated by the feed or cycle-controlling mechanism and the third arm engaging intermittently with dogs on the said member to move the lever, disengage the clutch and re-charge a spring for oscillating the lever again when released. In one form, a power shaft 24 has gears 23, 25, 26 secured thereon which engage loose gears 22, 27, 28 on a shaft 21 which drives the lathe spindle. The gear 22 has an over-running free wheel so that adjustment of a clutch 20 to either extreme position or to the intermediate position shown gives a three-speed change to the shaft 21. The clutch 20 is controlled by a connecting rod 15 actuated by a crank 14 on a disc 10, (constituting the said member), which carries a bevel gear meshing with a pinion 7 loose on a shaft 4 continuously rotated by the power-driven shaft 1. The pinion 7 is intermittently coupled to the shaft 4 to move the clutch 20 by means of a clutch 5 actuated by a slidable member 48 which is operated by a three-armed lever 38, 44, 51. A locking lever 37 normally rests against the arm 38 to maintain the clutch 5 disengaged as shown, but when a dog 30 on a disc 29, continuously driven by the feed gear of the machine, engages a trip 31 on the lever 37, the trip first yields against a spring 33 and then engages an abutment 35 on the lever to rock it against a spring 36 and release the arm 38. A spring 40 then oscillates the arm 38 and causes its end to wipe over an inclined portion 41 on the lever 37 to move the trip 31 out of the path of the dog 30. Simultaneously the arm 44 acts on a rod 45 within the member 48 to couple the pinion 7 to the shaft, thereby causing the clutch 20 to change the gear of the spindle drive, a spring catch 52 engaging the end 53 of the member 48 to hold the clutch 5 in engagement. When the clutch 20 has been moved the requisite distance, a dog 13 on the disc 10 engages the arm 51 to oscillate the three armed lever 38, 44, 51. The catch 52 continues to hold the member 48, until its slotted end is engaged by the pin 56 on the arm 38, whereupon a spring 46 shoots the clutch 5 out of engagement with the pinion 7 to stop rotation of the disc 10. As soon as the dog 13 has passed the end of the arm 51 the spring 40 returns the arm 38 into contact with the locking lever 37, and the arm 51 projects behind the dog as shown. The other dogs 30 on the disc 29 come into action successively to move the clutch 20 into its other positions. In a modification providing nine speed changes, a power driven shaft 24, Fig. 3, has the gears shown secured thereto and meshing with loose gears on the spindle-driving shaft 21. The disc 10 is capable of being moved successively into nine positions by the feed gear and is connected by the rod 15 to the slidable shaft 21 which carries a spring key 60 engageable with each of the loose gears in turn. Discs 64 with chamfered bores are placed between the loose gears to ensure the key 60 being completely removed from one gear before it is engaged with the next. Idler gears may be provided between some of the pairs on the shafts 21, 24 in order to provide one or more reverse drives. The locking lever 37 may be operated by a hand-controlled button 63, Fig. 1, for determining the relative positions of the dogs on the discs 10 and 29 in setting up the machine.